A “sliding” rotary vane compressor is a positive displacement machine that uses a rotor, which may be, but is not necessarily, eccentric, placed within a cylindrical chamber that is located within a rotor housing and is used to compress compressible fluids such as gases. The rotor has slots along its length, and each slot contains a blade, i.e. a vane. The vanes are thrown outwards by centrifugal force when the compressor is running and the vanes move in and out of the slot and follow the contour of the inner chamber wall. The vanes create individual cells of gas which, because of the vanes' movement, are compressed as the rotor turns. The vanes sweep the cylinder, sucking air in on one side and ejecting it on the other. As each cell approaches the discharge port, its volume is reduced and the compressed fluid is discharged.
A major concern with sliding vane compressors is discharge temperature, which must be controlled within reasonable limits to avoid serious mechanical damage to the compressor. Uncontrolled discharge temperature can lead to thermal growth of internal components causing jamming, internal components degrading or melting and lubrication failure. In addition, it is prudent to maintain discharge temperature of oil lubricated sliding vane compressors to about no greater than 350° F., although discharge temperatures lower than that are certainly desirable to minimize the disadvantages listed above, to limit the risk of oil fire. Furthermore, another practical limitation for oil lubricated and oil free compressors is the composition of the blade material. For example, the maximum temperature limits for resin bonded blade materials is also about 350° F., although some premium blade materials allow operation at slightly higher temperatures.
Oil drip lubricated and oil free sliding vanes follow the rules of isentropic compression, in which no heat is removed as the volume of the fluid is reduced and the pressure of the fluid rises. Gasses naturally heat when the volume is reduced and the pressure rises, and the greater the compression ratio, defined as the absolute outlet pressure divided by the absolute inlet pressure, the greater the outlet temperature.
Typically fluid is pulled into the compressor at the inlet at atmospheric pressure. The compression ratio of the compressor and discharge temperature of the compressor can be decreased, and the capacity of the compressor can be increased, if the fluid is inserted at the intake under pressure. This requires both larger size equipment and significally more power output since all of the air entering the intake must be pre-compressed. This is a more energy intensive solution than the proposed invention.
It is therefore an object of this invention to have a rotary vane compressor that provides increased capacity without a corresponding increase in size, decreased compression ratios and decreased fluid discharge temperatures with minimal increases in power requirements.